Please Say It Isn’t So, National Geographic

Published September 8, 2004

Like most young people growing up in the 1940s and 1950s, I depended on National Geographic to satisfy my curiosity of the world around me. It was a major reason why I chose a career in science.

So I was disappointed to see the great magazine of my youth compromise its reputation by taking an obviously politically motivated position on the issue of global warming. For me this fall from grace was tantamount to the time long ago when I learned the truth about Santa Claus.

National Geographic’s September issue contains a lavishly illustrated 74-page feature on climate change that focuses entirely on bits and pieces of data that seem to support the theory that human activity is causing global warming. No mention is made of the many prominent scientists who say we know too little to make this attribution or to predict future climate change.

On a global level, when all the earth’s ice is measured, we find as much is thickening as is thinning. Similarly, when we ignore short-term regional trends and focus on global temperatures as measured by satellites, no warming trend is found. We have plenty of anecdotes that seem to suggest climate change, but little evidence or proof that warming is happening on a global scale or that mankind is responsible for it.

The gases that absorb the infrared radiation and create the greenhouse effect are mainly water vapor, carbon dioxide, methane, and nitrous oxide. Water vapor and water in clouds absorb nearly 90 percent of the infrared radiation, while carbon dioxide, methane, and the other minor greenhouse gases together absorb little more than 10 percent of the infrared radiation.

Therefore, most of the greenhouse effect is natural and caused by the different forms of water in the atmosphere. However, human activities over the last 100 years – such as burning wood, coal, oil, and natural gas – have increased the concentration of greenhouse gases in the atmosphere by an amount equivalent to a forty percent increase in carbon dioxide alone. This is an increase of only two per cent in total greenhouse gases.

We know from simple physics that the additional energy added to the climate system by the doubling of atmospheric CO2 is about 4 watts per square meter (W/m2) – a small amount of energy compared to the 342 watts per square meter added by the sun’s radiation at the top of the atmosphere, and small too compared to natural variations in that source of radiation.

The possible increase in energy stored in the atmosphere due to human activity is also small compared to uncertainties in the computer simulations of the earth’s climate used to predict global warming. For example, knowledge of the amount of energy flowing from equator to poles is uncertain by an amount equivalent to 25-30 W/m2. The amount of sunlight absorbed by the atmosphere or reflected by the surface is also uncertain by as much as 25 W/m2. Some computer models include adjustments to the energy flows of as much as 100 W/m2. Imprecise treatment of clouds may introduce another 25 W/m2 of uncertainty into the basic computations.(2)

These uncertainties are many times larger than the 4 /m2 input of energy resulting from a doubling of CO2 concentration in the atmosphere. It is difficult to see how the climate impact of the 4W/m2 can be accurately calculated in the face of such huge uncertainties. As a consequence, forecasts based on the computer simulations of climate may not even be meaningful at this time.

National Geographic’s decision to present only the alarmist perspective on this important issue means it missed an opportunity to truly educate its readers. Most of us laughed at the absurd science fiction displayed in this summer’s global warming movie, “The Day After Tomorrow.” Seeing similar mistakes and exaggerations appear in a respected magazine is no laughing matter.

Dr. Jay Lehr is science director of The Heartland Institute and editor of several leading scientific reference books, including McGraw-Hill’s Handbook on Environmental Science, Health and Technology.